1. Field of the Invention
The present invention relates to a photosensitive dispersion with adjustable viscosity for depositing metal on an insulating substrate and use thereof.
2. The Prior Art
The patent EP 0 687 311 of the applicant concerns a polymeric resin with adjustable viscosity and pH for depositing catalytic palladium on a substrate, comprising, in combination, a palladium salt, a sequestering agent of the chloride or carboxylic acid type, a polymer containing hydroxyl and/or carboxyl groups soluble in water, a basic compound and a solvent chosen from amongst water, methanol and ethanol, the pH value being between 1 and 10, and to its applications for the deposition of catalytic palladium on the substrate surface and for the metallisation of these surfaces. Although this type of polymeric resin with palladium has proved advantageous in a large number of applications in the metallisation of polymeric substrates and the like, in particular because of its stability over time and the adjustability of its viscosity and pH, it does however have a certain number of drawbacks, including the obligatory use of palladium, which is a noble metal that is both expensive and whose price fluctuates greatly on the market, and the obligatory passage through an autocatalytic (electroless) bath for the metallisation of the non-conductive substrate and also because of the fact that the photosensitivity of the resin is reduced to a narrow range of wavelengths lying between 190 and 300 nm, thus greatly limiting the type of application that can be envisaged and the radiation source that can be used in this regard.
One of the essential aims of the present invention consequently consists of remedying the aforementioned drawbacks and presenting a photosensitive dispersion with adjustable viscosity that no longer necessarily requires the use of a noble metal such as palladium and also having recourse to other more common and less expensive metals and whose photosensitivity is broadened to a range of wavelengths between 190 and 450 nm requiring much lower irradiation energy than the polymer resins known up till now, below 100 mJ/cm2, and not requiring the obligatory passage through an autocatalytic bath for metallising the substrate, consequently allowing direct electrolytic metallisation.